A load sensing control circuit described in JP2004-239378A is available in the prior art.
In the load sensing control circuit described in JP2004-239378A, a fluid discharged from a variable displacement pump is divided, whereupon the divided fluid is supplied to a first actuator via a first switch valve and a first compensator valve, and to a second actuator via a second switch valve and a second compensator valve. Further, a higher maximum load pressure of maximum load pressures in head side chambers of the respective actuators is selected and led to a regulator provided in the variable displacement pump, whereupon a discharge amount of the variable displacement pump is controlled in accordance with the maximum load pressure led thereto. The first compensator valve and the second compensator valve function to keep a flow dividing ratio determined in accordance with respective openings of the first switch valve and the second switch valve constant even when a load pressure of the first actuator or the second actuator varies.